Power supply having a plurality of light emission units

Abstract

A power supply is provided. The power supply includes a plurality of light emission units, a power source, a plurality of boards, a plurality of board resistors, and a feedback control unit. The light emission units are connected in parallel, and include a plurality of LEDs. The power source supplies a DC voltage to the light emission units. The boards have at least one light emission mounted thereon. The board resistors are disposed in each of the boards, and electrically connected to each other. The feedback control unit varies a current supplied from the power source, according to sum of the board resistors which are changed according to the number of connected boards.

The invention claimed is: 
     
       1. A power supply comprising:
 a plurality of light emission units connected in parallel, and comprising a plurality of Light Emitting Diodes (LEDs); 
 a power source supplying a Direct Current (DC) voltage to the light emission units; 
 a plurality of boards having at least one light emission mounted thereon; 
 a plurality of board resistors disposed in each of the boards, and electrically connected to each other; and 
 a feedback control unit varying a current supplied from the power source, according to sum of the board resistors which are changed according to the number of connected boards, 
 wherein the feedback control unit comprises:
 a resistor connected to a reference voltage; 
 a reference potential unit outputting a voltage-divided value which is obtained through voltage division by the resistor and the board resistor; and 
 a comparator comparing an output of the reference potential unit and a value of an output terminal in each of the light emission units to output a signal to the power source according to the compared result, thereby controlling an output current of the power source. 
 
 
     
     
       2. The power supply according to  claim 1 , wherein the LEDs of each of the light emission units are serially connected to each other. 
     
     
       3. The power supply according to  claim 1 , wherein the board resistors are connected to each other in parallel. 
     
     
       4. The power supply according to  claim 1 , wherein the board resistors of each of the boards are electrically disconnected from the LEDs. 
     
     
       5. The power supply according to  claim 1 , wherein the feedback control unit comprises a current regulator connected to an output terminal of each of the light emission units and the comparator, other end of the current control unit being connected to the power source. 
     
     
       6. The power supply according to  claim 1 , wherein each of the boards comprises a connector, the connector connecting the board resistors to each other in parallel. 
     
     
       7. The power supply according to  claim 1 , wherein a value of each of the board resistors is changed according to the number of connected boards, and the feedback control unit varies a current supplied from the power source, according to the change of the board resistance value. 
     
     
       8. The power supply according to  claim 1 , wherein the feedback control unit controls a constant current according to the number of connected boards. 
     
     
       9. The power supply according to  claim 1 , wherein the board resistors have the same resistance value. 
     
     
       10. The power supply according to  claim 1 , wherein the reference potential unit is connected to one end of the resistor and one end of the board resistor in parallel.